Rotating machine with at least one active magnetic bearing and auxiliary rolling bearings

Abstract

A rotating machine comprises a shaft, a casing, at least one main magnetic bearing connected to the shaft for rotatably supporting the shaft inside the casing, at least one auxiliary radial rolling bearing and at least one auxiliary axial rolling bearing which are disposed between the shaft and the casing to respectively support radial loads only and axial loads only.

What is claimed is: 
     
       1. A rotating machine comprising:
 a shaft; 
 a casing; 
 at least one main magnetic bearing connected to the shaft for rotatably supporting the shaft inside the casing; 
 at least one auxiliary radial rolling bearing and at least one auxiliary axial rolling bearing disposed between the shaft and the casing to respectively support radial loads only and axial loads only; and 
 a first sleeve mounted on the shaft and interposed between an outer surface of the shaft and an inner ring of the at least one auxiliary radial rolling bearing with a first radial clearance provided between the first sleeve and the inner ring of the at least one auxiliary radial rolling bearing, and a second sleeve mounted on the shaft and interposed between the outer surface of the shaft and an inner ring of the at least one auxiliary axial rolling bearing with a second radial clearance provided between the second sleeve and the inner ring of the at least one auxiliary axial rolling bearing, 
 wherein the second radial clearance is greater than the first radial clearance. 
 
     
     
       2. A rotating machine according to  claim 1 , wherein the radial rolling bearing is axially spaced apart from the axial rolling bearing. 
     
     
       3. A rotating machine according to  claim 1 , wherein the auxiliary rolling bearings are disposed axially next to the main magnetic bearing. 
     
     
       4. A rotating machine according to  claim 1 , comprising two radial rolling bearings axially in contact one to another and two axial rolling bearings axially in contact one to another. 
     
     
       5. A rotating machine according to  claim 1 , wherein each of the at least one radial rolling bearing is a deep groove ball bearing or a four-point contact ball bearing. 
     
     
       6. A rotating machine according to  claim 1 , wherein each of the at least one axial rolling bearing is an angular contact thrust ball bearing. 
     
     
       7. A rotating machine according to  claim 1 , further comprising at least one pre-stressing and damping element exerting an axial force on at least one of the radial and axial rolling bearings. 
     
     
       8. A rotating machine according to  claim 7 , comprising at least one pre-stressing and damping element exerting an axial force on each of the radial and axial rolling bearings. 
     
     
       9. A rotating machine according to  claim 7 , wherein a first pre-stressing and damping element is mounted on the casing and axially bears against an outer ring of the axial rolling bearing. 
     
     
       10. A rotating machine according to  claim 9 , wherein a second pre-stressing and damping element is mounted between the casing and the outer ring of the axial rolling bearing axially on the side opposite to the first pre-stressing element, the first and second pre-stressing and damping elements exerting two axial opposed forces on the axial rolling bearing. 
     
     
       11. A rotating machine according to  claim 7 , wherein a pre-stressing and damping element is mounted on the casing and axially bears against an outer ring of the radial rolling bearing. 
     
     
       12. A rotating machine according to  claim 1 , wherein the at least one radial rolling bearing is a four-point contact ball bearing.